The present invention relates to a device used for rotating disk shaped data carriers inside of disk player and/or recorders.
A disk player and/or recorder is used to read and/or write on disk shaped data carriers. Different types of disk shaped data carriers are known, e.g. magnetical and optical disk shaped data carriers. Data may be stored along tracks which form for example concentrical circles or a spiral on the disk shaped data carrier. The disk shaped data carriers typically have an opening at a center, which ideally has substantially a common center with the disk shaped data carrier and the concentrical circles or the spiral. The disk shaped data carrier is rotated by driving means which are linked directly or indirectly to its opening, i.e. the driving means' rotation axis is made to correspond with the center of the disk. The data is read using reading means which follow the track. A servo system determines if the reading means deviate from the track being followed and if necessary move the reading means to reposition them on the track. The better the driving means' rotation axis corresponds to the center of the disk, the better the concentrical circles or spiral rotate around their own center and the less the servo system has to correct deviations to compensate for an eccentricity of the concentrical circle's or the spiral's rotation.
A data reading and/or writing rate of a disk player and/or recorder depends for a part on a disk's rotation speed. The reading and/or writing rate may for example be increased with a higher rotation speed of the disk. Typically a new problem arises in the disk player and/or recorder at higher rotation speeds. The player and/or recorder starts to vibrate, become more noisier and eventually to generate a greater number of reading and/or writing errors because the servo system may not anymore keep the reading means on track.
One reason for the new problem lies in the mass distribution of the disk shaped data carrier and parts fixed to it during its rotation. More precisely a mass center of the disk shaped data carrier and parts fixed to it may be located aside of the rotation axis imposed by the driving means and, as a result, the rotation of the disk generates forces which draw the disk away from the imposed rotation axis. The displacement of the mass center can be caused by labels on the disk, imperfect manufacturing of the disk, erroneous centering of the opening or other reasons. But it may also be related to the disk player and/or recorder itself.
A known solution to overcome the problems related to higher rotation speeds is to reduce the rotation speed until an acceptable level of noise, vibration and/or number of reading/writing errors is achieved. This of course reduces the data reading and/or writing rate.